1. Field of the Invention
The present invention relates to the technical field of a digital image scalar-up circuit and, more particularly, to an edge enhancement method and an edge enhancement apparatus in digital image scalar-up circuit.
2. Description of Related Art
Typically, the basic method of scaling-up a digital image is to reference the illuminations of neighbor pixels and use, for example, the nearest neighbor, bilinear, quadratic, bi-cubic or look-up table with interpolation methods for generating the new pixels. FIG. 1 shows part pixels of an image, wherein pixels P1˜P9 are existed pixels and pixels I1˜I8 are new pixels to be generated in scaling up process. The pixels I2 and I3 are in the distance of the pixel P5 as shown by the dashed line. The illuminations of these two new pixels I2 and I3 can be derived from the illuminations of the original pixels P1˜P9 in combination with the relative distance (Ix, Iy) from the pixel P5. In the calculating process, the coefficients of the polynomial are determined first according to the illumination information of pixels P1˜P9. Then, the illuminations of I2 and I3 are derived from the interpolation method according to the distance (Ix, Iy). In the implementation circuit, the pixels P1, P2 and P3 are in the same line, the pixels P4, P5 and P6 are belonged to the next line, and the pixels P7, P8 and P9 are belonged to the next two lines. Therefore, in order to obtain the information of pixels P1˜P9 simultaneously, it needs to implement registers in the circuit that can store information of the two line. Thus, if the original image resolution is 1024×960 (horizontal× vertical), a total number of 1024×2 registers is required.
Although the aforementioned interpolation method can increase the resolution of the image, it also blurs the profile of the image. Therefore, a subsequent edge enhancement process is required to reduce the blurring phenomenon of the image. However, the edge enhancement process also needs extra memory registers, resulting in exhausting the memory resource. Therefore, there is a desire to have a novel design for scaling up digital image with limited memory that can mitigate and/or obviate the aforementioned problems.